HY USMLE Q #782 – Pathology

A 69-year-old man is brought to emergency because of severe abdominal pain for the past 4 hours. He has a history of chronic atrial fibrillation. Abdominal examination shows mild diffuse tenderness to palpation. Fecal occult blood is positive. Laboratory studies show:

Hemoglobin                                                     14 g/dL
WBC                                                                     12,000/μL
pH                                                                           7.2
pCO                                                                    25 mm Hg
pO2                                                                        85 mm Hg

Which of the following is the most likely diagnosis?

  Abdominal aortic aneurysm
  Diverticulitis
 Gastroenteritis
  Ischemic colitis
  Mesenteric ischemia
  Perforated ulcer